Ozone ice in which ozone gas is contained as gas bubbles in ice has been used for refrigerating perishables, primarily fresh food products such as fresh fish and vegetables, and also for sterilization, disinfection, and odor elimination. Since the ozone gas self-decomposes into oxygen and causes no secondary contamination, it has attracted attention as a substitute for other sterilizing agents such as chlorine-containing sterilizing agents.
Methods for manufacturing ozone ice that have been heretofore considered can be generally classified into two groups. The first group includes methods by which water including ozone gas as gas bubbles is cooled and frozen (see, for example, Japanese Patent Application Publication No. 2005-77040 (Patent Publication No. 4052465), and the second group includes methods by which an ice powder is compressed, while ozone gas is being supplied thereto (see, for example, Japanese Patent Application Publication No. H3-186174).
Japanese Patent Application Publication No. 2005-77040 (Patent Publication No. 4052465) describes a method for producing ozone ice by which ozonized water having ozone dissolved therein is cooled and frozen in a pressurized state. Japanese Patent Application Publication No. H3-186174 describes a method for producing ozone ice by which snow is placed into a container, air, contained inside the container is removed, and compression is performed, while pumping ozone gas into the container.
Japanese Patent Application Publication No. 2006-145141 describes a method for producing ozone ice by cooling and freezing ozonized water produced by electrolysis. Japanese Patent Application Publication No. 3375904 and Non-Patent Document 1 “Electrolytic Generation of Available Chlorine and Ozone for Sterilization by Use of Noble Metal Electrode”, KONDO Yasuhito, KOIZUMI Yurika, ISEKI Masahiro, YAMADA Atsushi, TAKAOKA Daizo, TAKIZAWA Kikuo, YASUDA Masashi, IMAI Hachiro, HYOMEN GIJUTSU (The Journal of the Surface Finishing Society of Japan), Vol. 56, No. 2, 34-40, 2005 describe methods for producing high-concentration ozonized water in an anode by optimizing electrodes of an electrolytic cell used in the electrolysis and the components of water used as a starting material.
However, with the conventional method for cooling and freezing water including ozone gas as gas bubbles and method for compressing an ice powder, while supplying ozone gas thereto, since ozone gas decomposes within a short time into a more stable oxygen gas, the ozone ice should be stored at a temperature sufficiently lower than the melting point thereof, and storage stability of the produced ozone ice is important. Therefore, with the conventional methods, it is difficult to maintain the sterilization effect of ozone ice over a long period.